Means for controlling the tension in running strip



J. L. PACKER ET AL Jan. 26, 1954 MEANS FOR CONTROLLING THE TENSION IN RUNNING STRIP Filed Oct. 17, 1951 3 Sheets-Sheet 1 "IL. 7%CAL/L/ g-AW Attorney Jan. 26, 1954 J. L. PACKER ET AL 2,667,311

MEANSWLOj CONTROLLING THE TENSION IN RUNNING STRIP Filed Oct. 1'7, 1951 5 Sheets-Sheet 2 Attorney Jan. 26, 1954 J. L. PACKER ET AL MEANS FOR CONTROLLING THE TENSION IN RUNNING STRIP Filed Oct. 17, 1951 3 Sheets-Sheet 3 range than in others.

also applicable to other about the conductor.

Patented Jan. 26, 1954 MEANS FOR CONTROLLING THE TENSION 'IN RUNNING STRIP Sevenoaks, and George Johnson Lewis Packer,

Thomas 'Wilson Grie Woolwich, London,

England, assignors to British Insulated Callenders CablesLiniitcd, London, England, a British company Application'october 17, 1951, Serial No. 251,784

(llaimspriority, application Great Britain October 27, 1950 7 Claims. (01. 242 75) 1 When a strip of paper or other material is being drawn from or wound 'on to a reel, bobbin or other support, there is frequently the necessity "for keeping the tension in the member approximately constant.

Some cases require a greater degree of accuracy and constancy in this than others and in some cases there is more'tendency to variation of tension and variation over a larger One of the most difficult cases, from both these points of'view, is found in the lapping of paper tape on to an electric conductor for the purpose of building-up abody of insulating material. It'is with this case that the invention is primarily concerned but it is cases.

Inlapping paper tape on to an electric conductor the tape in the form of a flat spiral coil or pad is held on a spindle between discs and the whole is rotated about the axis of the cable, the paper tape being drawn ofi over suitable guides so as to be lapped helically with precision Tension is applied to the tape at the pad holder by bearing friction and by a brake. It is also applied by friction at the guides. The total tension is produced by a combination of these effects in varying proportions according to the design of machine and to the particular conditions of operation.

One of the principal causes operating to produce variation'in the tension in the paper is the change in the diameter of the pad. A constant tension in the paper at the periphery of the pad obviously cannot be balanced by a constant braking force on the pad carrier, since the radius of the application of tension varies through a large range.

The present invention provides an improved means for adjusting the load on the brake, which acts on the support for the coil of strip, as the tension in the strip varies, with "the object of exerting a correcting influence-and maintaining the tension approximatelyconstant. The principal element of :the improved means is a chamber which is supplied with compressed :air or other gas through a controlled gas-leakage aperture and which loses the -:gas through a nozzle having an aperture over-which the strip passes and against the edges of which the strip is held by the tension in it. 'It.is found that with such a device the pressure in the chamber has a definite relation to the tension in "the strip, the greater the tension the. lessis the rate of leakage and, accordingly, the higher-is the pressure in the chamber.

This pressurezcan -beused :forthe purpose of adjusting the load on the brake, 'for instance by makingthe chamber in the form'of a cylinder in which works a piston or diaphragm connected through a relay to the brake. The combined effect of a spring and the pressure-and the relay enables the required adjustment to be obtained with marked sensitivenessand closeness of .control.

The'relays may be of the pneumatic kind fed at a pressure controlled by the pressure in the chamber. This may be done by-causing the chamber tobe made in the form of asmall cylinderin which works a piston or "diaphragm moved in one direction by a spring and in the other direction by the pneumatic pressure in the chamber. The movement of this piston or diaphragm may regulate the pressure applied to the relay by moving a valve which adjusts the size of'za second gas leakage aperture'in'the pipe supplying the brake relay from a source of constant pressure fluid. Other types of relay may, however, be used, for instance an electric relaypand other methods of control from the pneumatic chamber maybe employed.

The invention is further describedwith referonce by way of example to the accompanying drawings which illustrate diagrammatically "an arrangement incorporating the improved device. In these drawings:

Figure 1 is an end view of the nozzle, and'illustrates the relative dimensions-of the outlet and the paper strip;

Figure 2 is a view in elevation arrangement; 4

Figure 3 is a 'viewinpart section of a portion of the arrangement shown in Figured-but to a larger scale;

Figure 3a is a view of part of the arrangement shown in Figure 3 as seen in'the direction'of the arrows on the line IIIAIIIA;

Figure 4 is a sectional view' on the line IV-IV in Figure 2, taken in the direction ofthe arrows in that figure.

The arrangement shown is a tension-controlling device in which a pneumatic relay is employed 'for regulating the tension in a strip I of paper as it is drawn from a reel '2 in apaper lapping machine. The reel 2 is rotatably mounted on a spindle 3 which is itself carried on a support 4 extending parallel with the machine axis. An electric conductor to be'lapped with paper will be drawn through the machine axis in the usual way, and the paper strip helically applied as the support 4 is carried round the conductor on a carrier disc 5 "supof the improved through the spindle 1. By means of a liner 8 there is formed within the spindle 1 a passage 9 which is adapted to be maintained filled with 7 air under pressure from a source not shown. The pierced with a ring of wall of the spindle 1 is apertures II] communicating with the inside of an annular chamber |I formed in a casing I2 which surrounds the spindle 1. The casing, I2 is mounted on ball bearings I3 so as to be freely rotatable about the spindle 1. From the casing I2 there extend two pipes I4 and I5 over which air under pressure is led from the annular chamber II to the various components of the tension controlling device as the latter is carried round the spindle 1. 7

Referring particularly to Figure 4, the reel 2 of paper is mounted on a central hollow boss I6 which itself is rotatably supported on the end I8 of the spindle 3 by means of ball bearings I1. The spindle 3 is non-rotatably fixed in the support 4 by a nut I9. The reel 2 is tightly gripped between a brake disc fixed to the boss I6, and a removable disc 2|. The brake disc 20 is fastened to the side of the boss I6 by bolts I23, and the removable disc 2| is held in place by a locking ring 22 which engages a screw-thread on the outside of the boss I6. An annular friction disc 23 is adapted to be pressed against the outer surface of the brake disc 20 to supply the necessary braking force. The friction disc 23 is fixed to a rigid supporting ring 24 mounted on a spider 25 which extends radially from a central boss I30. This boss I is fixed to the spindle '3 and the spider 25 while being sufficiently rigid to maintain the correct annular position of the supporting ring 24, is sufllcient- 1y flexible to permit a limited movement of the ring in a direction parallel with the spindle axis.

On the opposite side of the friction disc 23 to the brake disc 29 there is provided a shallow annular pressure chamber 21. This chamber 21 is formed by a rigid radially extending wall 26 having at its outer edge a flange 29 extending parallel with the axis and towards the brake disc 20 and a diaphragm 28 extending parallel with the wall 26. The outer edge of the diaphragm is attached in an air-tight manner to the flange 29, and the inner parts phragm 28 and the wall 26'make air-tight connection with the spindle 3. The outside of the diaphragm 28 is in contact with the back of the supporting ring 24 so that pressure exerted on the diaphragm in the pressure chamber 21 is transmitted to the friction disc 23, tending to force this disc into engagement with the brake disc 20, and thereby exert the necessary braking force on the reel 2. Compressed air enters the pressure chamber 21 from the branch pipe |5 through a three-way junction 38. The body of the three-way junction 39 is fixed to the end of the spindle 3, and a passage 3| extends from the junction 38 through the centre of the spindle. From the inner end of the passage 3| there extend radial apertures 32 which terminate in slots or key-ways 33 formed in the surface of the spindle 3. The key-ways 33 communicate with passages 34 leading into the pressure chamber 21.

From the three-way junction 38 a pipe 35 is connected to a second gas-leakage aperture 35 which is in the form of a valve seating. Also incorporated in the junction 38 there is an adjustable throttle valve 31 adapted to be pre-set of the diato control the flow of air under pressure from the pipe I5 into the pressure chamber 21. The aperture 36 is adapted to be closed by a valve 38. The position of this valve with reference to the aperture 36 is determined by a pneumatic relay 39. Maximum braking pressure on the reel 2 is obtained when the aperture 36 is closed completely by the valve 38 so that air under pressure fed from the pipe I5 into the pressure chamber 21 is not allowed to escape. By withdrawing the valve 38 from the seating around the aperture 36, air is allowed to escape from the pressure chamber 21 through the pipe 35. The consequent reduction of pressure in the pressure chamber 21 depends upon the amount of the opening of the valve 38, and the ultimate braking force is reduced to a minimum when the valve 38 is fully open.

The pneumatic relay 39 comprises two chambers 48 and 4| separated by a central partition 42, and each closed by a flexible diaphragm 43. The valve 38 is fixed to the end of a valve stem 44 which passes through the diaphragms 43 and the partition 42. The valve stem is fixed to both diaphragms 43 and is a sliding fit in the partition 42. The connections between the rod and the diaphragms and the partition are substantially air-tight. Associated with the relay 39 is a slide valve comprising a piston 45 adapted to slide within an open-ended sleeve 46. Into the central region of the sleeve 46 compressed air is led from the pipe I4 through a throttle valve 41 and a pipe connection 48. From the lefthand end of the sleeve 46 there is a pipe connection 49 to the left-hand relay chamber 48. There is a similar pipe connection 50 between the righthand end of the sleeve 46 and the right-hand relay chamber 4|. The ports at the entries of the connections 49 and 50 into the sleeve 46 are completely closed by the valve faces on the piston 45 when it is in the central position as shown. In this position therefore there is no connection from either of the relay chambers 49 and 4| to the atmosphere. The valve faces on the piston 45 are only slightly broader than is necessary to close the ports. The central portion of the piston 45 is waisted to form an annular chamber into which compressed air is fed from the central pipe connection 48. Also from the pipe I4 there is a pipe connection through an adjustable throttle valve 5| and a pipe 53 to a pneumatic chamber 52, and to a nozzle 54 over a pipe 55. The pneumatic chamber 52 comprises a rigid end wall 56, and parallel therewith another wall in the form of a flexible diaphragm 51. The stem 58 of the slide valve piston 45 extends through the wall 56 and the diaphragm 51. The stem 58 is connected to the diaphragm 51, and is supported so as to be a sliding fit in the wall 56, all the connections between the valve stem 58, the wall 56 and the diaphragm 51, being substantially air-tight. A spring 59 engages the end of the valve stem 58. The spring 59 is carried on a clip 200 embracing an extension 20| of the support 4. The pressure of the spring 59 may be adjusted by altering the position of the clip. The nozzle 54 is a tapered member, presenting to the paper I which passes over it a contact surface which is narrow in the direction of movement of the paper. The nozzle 54 is associated with two guide pulleys 60 and BI, arranged one on each side of the nozzle and in such positions that in its passage over the nozzle the path of the paper is deflected a few degrees. In the surface of the nozzle with which the paper engages is a gas-leakage aperture I59 which is narrow in the direction of movement of the paper, and the length of which is less than the width of the paper.

When the air pressure is applied to the sys tem described above, there will be a tendency for air to escape through the gas-leakage aperture I 59 thereby reducing the pressure in the pneumatic chamber 52, and there will also be a certain amount of escape of air through the other aperture 36 in dependence upon the setting of the valve 38. Initially the various throttle valves, together with the setting of the spring 59 and the valves 45 and 38 on the respective stems, are so adjusted that the braking force is appropriate for the required tension in the paper. As the diameter of the reel 2 decreases with consumption of the paper, the tendency is for the tension in the paper to increase. This reduces the rate of escape of air through the gas-leakage aperture I59 with consequent rise of pressure in the pneumatic chamber 52. 'The diaphragm 51 is moved against the pressure of the spring 59 so that the valve piston 45 moves towards the right-hand end of the sleeve 46. This movement opens the connection 49 to the atmosphere with consequent reduction in the pressure in the left-hand relay chamber 40. The same movement of the valve 45 exposes the end of pipe 50 to the supply of air from pipe 48, so that there is a tendency for the pressure to rise in the right-hand relay chamber II. In consequence of this change of pressure in the relay chambers 40 and AI, the valve 38 connected to the diaphragms 43 will move towards the right-hand away from the aperture 36. This increases the rate of leakage of air from the feed to the brake pressure chamber 21, thus reducing the pressure on the associated diaphragm 28 and friction disc 23. The braking force thus being reduced, the tension in the paper a strip I is lowered. When the tension again reaches the required value, the rate of leakage through the gas-leakage aperture I59 will again become normal so that the pressure in the pneumatic chamber 52 will return to the initial value. At this value the piston 45 will have again returned to the symmetrical position in which the ends of the pipes 49 and 50 are again closed. Due to the unbalanced pressure conditions which have been set up in the relay chambers 40 and 4|, the valve 38 will have acquired a fresh setting. It will be appreciated that the apparatus operates in the reverse manner in the event of the paper tension being decreased below the desired value so that the escape of air from the nozzle increases.

By the arrangement thus described the tension in the paper strip may be maintained substantially uniform or within the limits prescribed between predetermined maximum and minimum values. In this arrangement the various members, such as 38 and 45, which are movable in the tension-controlling operations are adapted to move in paths which are substantially parallel to the axis of the central fixed tube 1, so that there is freedom from the direct influence on the moving parts of centrifugal forces resulting from rotation of the device about that axis.

It will be appreciated that the diagrammatic description of an example is given by way of illustration of the invention and that, within the scope of the invention, many variations are possible in applying the pressure changes in the pneumatic chamber, such as the chamber 52, to the control of the braking force. For instance an alternative form of the brake-adjusting gear may be used. The'relay may be of a form appropriate for electrical or hydraulic operation. Furtherv more the valve parts may be of a variety of shapes depending upon the conditions under which they are to work and upon the precise effects desired. For instance, the valve 38 may present a flat face to the appropriately shaped valve-seating, or it may be in the nature of a needle-valve. Also, the brake pressure chamber 21 may be used in conjunction with a spring adapted to apply the braking force, the association being such that the force exerted by the spring is reduced with increasing pressure in the chamber. In this case the arrangement would be such that the valve 38 would be brought closer to itsseating with increasing tension in the strip.

What we claim as our invention isi l. A strip-feeding device comprising a rotatable support for a reel of strip, adjustable braking means for brakingthe support when rotated by withdrawal of strip from a reel mounted thereon,

a'pneumatic chamber having an entry for compressed gas and a gas leakage aperture for the escape of gas therefrom, guiding means for directing the strip in a path over and in contact with the leakage aperture, and a brake-adjusting relay connected with the pneumatic chamber and re sponsive to pressure changes therein brought about by variation in tension of strip in contact with the leakage aperture.

2. A strip-feeding device comprising a rotatable support for a reel of strip, adjustable braking means for braking the support when rotated by withdrawal of strip from a reel mounted thereon, a pneumatic chamber with an entry for gas under pressure and a gas leakage aperture, guiding means for directing the strip in a path across and in contact with the leakage aperture, a member within the pneumatic chamber movable in accordance with variation of pressure in the chamber, and a brake-adjusting relay connected with the movable member.

3. A strip-feeding device comprising a rotatable support for a reel of strip, adjustable braking means for braking the support when rotated by withdrawal of strip from a reel mounted thereon, a pneumatic chamber with an entry for gas under pressure and a gas leakage aperture, guiding means for directing the strip in a path across and in contact with the leakage aperture, at least one wall of the pneumatic chamber being a re siliently biased diaphragm movable in accordance with the variation of pressure in the chamber, and a brake-adjusting relay connected with the diaphragm.

4. A strip-feeding device comprising a rotatable support for a reel of strip, adjustable braking means for braking the support when rotated by withdrawal of strip from a reel mounted thereon, a pneumatic chamber with an entry for gas under pressure and a gas leakage aperture, guiding means for directingthe strip in a path across and in contact with the leakage aperture, a piston movable in the pneumatic chamber in accordance with variation of pressure therein, and a brake-adjusting relay connected with the piston.

5. A strip-feeding device comprising a rotatable support for a reel of strip, adjustable braking means for braking the support when rotated by withdrawal of strip from a reel mounted thereon, a pneumatic chamber with an entry for gas under pressure and a gas leakage aperture, guiding means for directing the strip in a bath across and in contact with the leakage apering means for braking the support When rotated I by withdrawal of strip from a reel mounted thereon, a pneumatic chamber with an entry 'for gas under pressure and a gas leakage aperture, guiding means for directing the strip in a path across and in contact with theleakage aperture,

a member within the pneumatic chamber movable in accordance with variation of pressure in the chamber, a pneumatic relay chamber with an entry forcompressed gas and a second gas-leakage aperture, an adjustable valve for the second gas-leakage aperture connected With the movable member whereby the rate of escape of gas from the relay chamber is variable with movement of the movable member, and aconnection between the pneumatic relay chamber and the adjustable brake for adjusting the brake in accordance with the pressure in the pneumatic relay chamber. 7

'7. A strip-feeding device comprising a rotatable support for a reel of strip, adjustable braking means for braking the support, when rotated by withdrawal of strip from a reel mounted thereon, a pneumatic chamberand a gas leakage aperture for the escape of gas therefrom, guiding means for directing the strip over and in con tact Withthe leakage aperture, a brake-adjusting relay connected with and responsive to pressure changes in the pneumatic chamber, a second pneumatic chamber having a flexible Wall, the said flexible Wall being adapted to apply the pressure in the said second pneumatic chamber tothe brake, and a valve adapted to control the pressure in the said second pneumatic chamber,

said valve being under the control of the brake adjusting relay.

JOHNSON LEWIS PACKER. GEORGE THOMAS WILSON GRIEVE.

lteferenees Cited in'the file of this patent UNITED STATES PATENTS V Number Name 7 Date 2,098,422 Keen et a l. Nov. 9, 1937 2,343,181 Heinz Feb. 29, 1%4 2,460,694 Haswell Feb. 1, 1949 2,462,558 Scheuermann et al. Feb. 22, 1949 2,472,548 Schnell June '7, 1949 

